The Geysers

{{Short description|World's largest geothermal field, California}} {{Use American English|date=July 2025}} {{Infobox power station | name = The Geysers | name_official = The Geysers | image = Sonoma Plant at The Geysers 4778.png | image_caption = The Sonoma Calpine 3 power plant is one of 18 power plants at The Geysers. | country = United States | location = Sonoma and Lake counties California | coordinates = {{coord|38|47|26|N|122|45|21|W|type:landmark_region:US-CA|display=inline,title}} | status = O | construction_began = | commissioned = September 1960<ref name=GBTN>{{Cite web|url=http://geysers.com/The-Geysers/Geysers-By-The-Numbers|title=Geysers By The Numbers|website=geysers.com|access-date=2020-02-02}}</ref> | decommissioned = | cost = | owner = Constellation Energy (86.5%) NCPA (4.5%) Silicon Valley Power (4.5%) USRG (4.5%) | operator = Calpine Corporation | employees =  | geo_type = Dry steam | geo_temp_requirement = | geo_well_count = 376 (active)<ref name=GBTN/> 591 (total)<ref name=GBTN/> | geo_well_depth = {{convert|12900|ft|m|abbr=on}}<ref name=GBTN/> | geo_water_output =  | ps_site_area = {{convert|29000|acres|km2}}<ref name=GBTN/> | ps_site_elevation = | ps_cooling_towers = | ps_feed-in_tariff = | ps_revenue = | ps_combined_cycle = | ps_cogeneration = | ps_thermal_capacity =  | ps_units_operational = 22 units (18 power stations) | ps_units_manu_model = | ps_units_planned = 3 units | ps_units_cancelled = | ps_units_uc = | ps_units_decommissioned = 7 units (4 power stations) | ps_electrical_capacity = 1,590 MW<ref name=OSTI2010>{{Cite journal|title=The Geysers Geothermal Field Update1990/2010|date=2010-10-01|series=OSTI 1048267|doi=10.2172/1048267|osti = 1048267|last1=Brophy|first1=P.|last2=Lippmann|first2=M.|last3=Dobson|first3=P.F.|last4=Poux|first4=B.|s2cid=129885237 |url=https://digital.library.unt.edu/ark:/67531/metadc832510/}}</ref> | ps_electrical_cap_fac = 53%<ref name=OSTI2010/> | ps_annual_generation = 6,516 GWh (2018)<ref>{{Cite web|url=https://www.eia.gov/electricity/data/browser/#/topic/1?agg=1,0,2&fuel=001&geo=000000000004&sec=g&freq=A&datecode=2018&rtype=s&start=200101&end=201911&ctype=map&ltype=pin&rse=0&maptype=0&pin=|title=Electricity Data Browser - List of plants for geothermal, California, all sectors|website=www.eia.gov|access-date=2020-02-02}}</ref> | ps_storage_capacity = | website = }} '''The Geysers''' is the world's largest developed geothermal field, containing a complex of 18 geothermal power plants, drawing steam from more than 350 wells, located in the Mayacamas Mountains approximately {{convert|72|mi|km}} north of San Francisco, California. Geysers produced about 20% of California's renewable energy in 2019.<ref>{{Cite web|url=https://www.yaleclimateconnections.org/2020/02/the-pros-and-cons-of-enhanced-geothermal-energy-systems/|title=The pros and cons of enhanced geothermal energy systems|last=McCarthy|first=Will|date=2020-02-06|website=Yale Climate Connections|language=en-US|access-date=2020-02-17}}</ref> The Geysers is owned by Constellation Energy, the largest nuclear and geothermal energy producer in the United States.

==History== thumb|The Geysers Resort Hotel, {{circa|1880}} For about 12,000 years, Native Americans built steam baths and thermal pools at The Geysers and used the steam and hot water for healing purposes, as well as spiritual and ceremonial practices, and cooking.<ref name="Hodgson">{{cite book|last=Hodgson|first=Susan F.|title=A Geysers Album: Five Eras of Geothermal History|year=2010|publisher=State of California Department of Conservation|location=Sacramento|url=ftp://ftp.consrv.ca.gov/pub/oil/publications/tr49.pdf| pages = 1–81 | access-date = February 9, 2014}}</ref> The thermal pools were used as a medicinal treatment for rheumatism and arthritis.<ref>{{Cite book |last=Nabokov, Loendorf |first=Peter, Lawrence |title=Restoring a Presence: American Indians and Yellowstone National Park |publisher=University of Oklahoma Press |year=2004 |isbn=9780806135892 |pages=277}}</ref> The heated mud was used to soothe skin rashes and other aches and pains, using the fumaroles as a natural energy source.<ref>{{Cite journal |last=Lund |first=John W. |date=October 1995 |title=Historical Impacts of Geothermal Resources on the People of North America |url=https://oregontechsfstatic.azureedge.net/sitefinity-production/docs/default-source/geoheat-center-documents/quarterly-bulletin/vol-16/art2.pdf?sfvrsn=4b3f8d60_4 |journal=GeoHeat Center Bulletin}}</ref>

When European Americans first arrived, six local native tribes inhabited the area around The Geysers. These tribes included three bands of Pomo people, two bands of Wappo people, and the Lake Miwok people.<ref name="Hodgson" /> The Wappo also collected sulfur which they called ''te'ke'' and a Wappo village, named ''tekena'ntsonoma'' (''teke'' sulphur + ''nan'' well containing water + ''tso'' ground + ''no'ma'' village) was located about {{convert|12|mi|km}} southeast of Cloverdale and on the present-day Sulphur Creek.<ref name="Hodgson" />

The Geysers were first seen by European Americans and named in 1847 during John Fremont's survey of the Sierra Mountains and the Great Basin by William Bell Elliot who called the area "The Geysers," although the geothermal features he discovered were not technically geysers, but fumaroles.<ref name="SAE">{{cite book|title=The Future of Energy: Earth, Wind and Fire|url=https://books.google.com/books?id=pGfQmBtXYx0C&pg=PT160|date=April 8, 2013|publisher=Scientific American |isbn=978-1-4668-3386-9|pages=160–|access-date = February 9, 2014}}</ref>

Between 1848 and 1854, Archibald C. Godwin developed The Geysers into a spa named ''The Geysers Resort Hotel'', which attracted tourists including Ulysses S. Grant, Theodore Roosevelt and Mark Twain.<ref name="Hodgson" /><ref name="SAE" /><ref>{{cite web| title = A History of Geothermal Energy in the United States| url = http://www1.eere.energy.gov/geothermal/history.html| publisher = U.S. Department of Energy| year = 2010| access-date = May 17, 2007| url-status = dead| archive-url = https://web.archive.org/web/20070904230627/http://www1.eere.energy.gov/geothermal/history.html| archive-date = September 4, 2007}}</ref> The resort declined in popularity in the mid 1880s, and rebranded itself to appeal to lower-income people.<ref name="Hodgson" /> In 1938, the main building was destroyed in a landslide although the bar/restaurant, small cabins and the swimming pool stayed open, despite another fire in March 1957, until about 1979.<ref name="Hodgson" /> In 1960, Pacific Gas and Electric began operation of their 11-megawatt geothermal electric plant at the Geysers. Unocal Corporation dismantled the remains of the resort in 1980.<ref name="Hodgson" />

The Geysers Geothermal Power Development project was designated as a California Historic Civil Engineering Landmark by the San Francisco Section of the American Society of Civil Engineers in 1976.<ref>{{cite news |last=Rintoul |first=Bill |title=Kern County oilfields news |work=The Bakersfield Californian |date=August 10, 1976 |page=20}}</ref>

Five of The Geysers facilities were damaged in the Valley Fire of September 2015, suffering "severe" damage to their cooling towers. The main power houses were not damaged.<ref>{{cite web| title = Valley Fire Devastates Facilities At The Geysers Geothermal Power Plant | url = http://sanfrancisco.cbslocal.com/2015/09/15/valley-fire-devastates-facilities-at-the-geysers-geothermal-power-plant/ | publisher=CBS Bay Area|year=2015|access-date=September 16, 2015}}</ref> The Kincade Fire started at John Kincade Road and Burned Mountain Road in The Geysers, at 9:27 PM on October 23, 2019.<ref name=":0">{{Cite web|url=https://www.latimes.com/california/story/2019-10-27/blackouts-take-effect-across-northern-california-as-kincade-fire-grows-winds-kick-up|title=Blackouts and mass evacuations as Kincade fire grows amid high winds|last1=Chabria|first1=Anita|last2=Dolan|first2=Maura|date=October 27, 2019|website=Los Angeles Times|language=en-US|access-date=October 27, 2019}}</ref><ref>{{Cite web|url=https://www.sfgate.com/california-wildfires/article/Map-Kincade-Fire-north-Sonoma-County-14559006.php|title=Map: Kincade Fire burning in north Sonoma County|last=Graff|first=Amy|date=2019-10-24|website=SFGate|access-date=2019-11-06}}</ref>

==Geothermal power stations== thumb|Drilling a geothermal well, 1977 (USGS) The Geysers is the world's largest geothermal field<ref name="GeoEnergy" /> spanning an area of around {{convert|30|mi2|km2}} in Sonoma, Lake and Mendocino counties in California, centered in the area of Geyser Canyon and Cobb Mountain. Power from The Geysers provides electricity to Sonoma, Lake, Mendocino, Marin, and Napa counties. It is estimated that the development meets 60% of the power demand for the coastal region between the Golden Gate Bridge and the Oregon state line.<ref name = "calpine">{{cite web| title = Calpine Corporation - The Geysers| url = http://www.geysers.com| access-date = 2008-06-11}}</ref> Unlike most geothermal resources, The Geysers is a dry steam field which mainly produces superheated steam.<ref name="GeoEnergy">{{cite book|last=Kagel|first=Alyssa|title=A Guide to Geothermal Energy and the Environment|publisher=Geothermal Energy Association|url=http://geo-energy.org/reports/environmental%20guide.pdf|author2=Diana Bates |author3=Karl Gawell |access-date=February 9, 2014}}</ref>

Steam used at The Geysers is produced from a greywacke sandstone reservoir, capped by a heterogeneous mix of low permeability rocks and underlain by a silicic intrusion.<ref name="SAE" /><ref>{{cite book|last=Enedy|first=Steve|title=Reservoir Response To Injection In The Southeast Geysers|year=1991|publisher=Sixteenth Workshop on Geothermal Reservoir Engineering|url=http://www.osti.gov/geothermal/servlets/purl/887486-8h0FCj/887486.pdf|author2=Kathy Enedy |author3=John Maney |access-date=May 16, 2007}}</ref> Gravitational and seismic studies suggest that the source of heat for the steam reservoir is a large magma chamber over {{convert|4|mi|km}} beneath the surface, and greater than {{convert|8|mi|km}} in diameter.<ref>{{cite web| title = Cascades Volcanic Observatory (USGS) - Clear Lake Volcanic Field, California| url = https://vulcan.wr.usgs.gov/Volcanoes/California/ClearLake/description_clear_lake.html| access-date = May 16, 2007}}</ref>

The first geothermal wells drilled in Geyser Canyon were the first in the Western Hemisphere.<ref name="Hodgson" /> The first power plant at The Geysers was privately developed by the owner of The Geysers Resort<ref name="Hodgson" /> and opened in 1921, producing 250 kilowatts of power to light the resort.<ref name="SAE" /> In 1960, Pacific Gas and Electric (PG&E) began operation of their 11-megawatt plant at the Geysers.<ref name="100years">{{Citation| last =Lund| first =J.| date =September 2004| title =100 Years of Geothermal Power Production| periodical =Geo-Heat Centre Quarterly Bulletin| location =Klamath Falls, Oregon| publisher =Oregon Institute of Technology| volume =25| issue =3| pages =11–19| url =http://geoheat.oit.edu/bulletin/bull25-3/art2.pdf| issn =0276-1084| access-date =April 13, 2009| archive-date =June 17, 2010| archive-url =https://web.archive.org/web/20100617221828/http://geoheat.oit.edu/bulletin/bull25-3/art2.pdf| url-status =dead}}</ref> The original turbine lasted for more than 30 years and produced 11 MW net power.<ref>{{Cite journal| last1 = McLarty| first1 = Lynn | last2 = Reed| first2 = Marshall J. | title = The U.S. Geothermal Industry: Three Decades of Growth| journal = Energy Sources, Part A: Recovery, Utilization, and Environmental Effects| volume = 14| issue = 4 | pages = 443–455 | publisher = Taylor & Francis | location = London | date = October 1992 | url = http://geotherm.inel.gov/publications/articles/mclarty/mclarty-reed.pdf | issn = 1556-7230 | doi = 10.1080/00908319208908739 }}</ref>

By 1999, the steam to power extraction had begun to deplete The Geysers steam field and production began to drop.<ref name="SAE" /> However, since October 16, 1997, The Geysers steam field has been recharged by injection of treated sewage effluent, producing approximately 77 megawatts of capacity in 2004.<ref name = "LakeCo">{{cite book|last=Dellinger|first=Mark|title=Geothermal and the Environment Lake County Success: Generating environmental gains with geothermal Power|date=May–June 2004|publisher=Lake County, California|url=http://geothermal.org/PDFs/Articles/lakeco.pdf|author2=Eliot Allen }}</ref> The effluent is piped up to {{convert|50|mi|km}} from its source at the Lake County Sanitation waste water treatment plants and added to the Geysers steam field via geothermal injection.<ref name = "LakeCo" />

The injection of wastewater to The Geysers protects local waterways and Clear Lake by diverting effluent which used to be put into surface waters,<ref name = "LakeCo" /> and has produced electricity without releasing greenhouse gases into the atmosphere. The Southeast Geysers Effluent Pipeline, completed in 1997, delivers approximately 9 million gallons per day of secondary treated wastewater through a 40-mile pipeline from Lake County communities. The Santa Rosa Geysers Recharge Project, completed in 2003, adds another 11 million gallons per day of tertiary treated effluent through a 42-mile pipeline. These projects provide approximately 20 million gallons of reclaimed water daily for injection into The Geysers reservoir, effectively converting wastewater into renewable electricity. The environmental benefits extend beyond energy production, as the projects have significantly reduced river discharges, with 65 percent of treated effluent from Santa Rosa, Rohnert Park, Cotati, and Sebastopol being consumed by the steam fields rather than discharged into the Russian River.<ref name="SAE" />

As of 2025, Calpine owned 13 units, most of which were acquired from PG&E and Unocal Geothermal in 1999. NCPA Units 1-4 are jointly owned by the Northern California Power Agency (NCPA) and Silicon Valley Power. Bottle Rock is wholly owned by Bottle Rock Power, a joint-venture between U.S. Renewables Group and Riverstone Holdings.<ref name=OSTI2010/>

In addition, Ormat owns the plans for a new 30 MW geothermal power station at the vacant Calpine 15 site that were acquired through a merger with U.S. Geothermal in 2018. The plans were previously developed by Ram Power before being sold to U.S. Geothermal in 2014.<ref name=OSTI2010/><ref>{{Cite web|url=https://investor.ormat.com/file/Index?KeyFile=393150291|title=Ormat Technologies Inc. - Press Release|website=investor.ormat.com|access-date=2020-02-17}}</ref><ref>{{Cite web|url=https://www.thinkgeoenergy.com/ram-power-becomes-polaris-infrastructure-inc/|title=Ram Power becomes Polaris Infrastructure Inc.|website=Think GeoEnergy - Geothermal Energy News|date=15 May 2015|language=en-US|access-date=2020-02-18}}</ref>

{{mw-datatable}} {| class="wikitable sortable mw-datatable" |- ! Name ! Unit ! Type ! Status ! Capacity (MWel) ! Commissioned ! Decommissioned |- | Bottle Rock || {{abbr|BRP|Bottle Rock Power}} || Dry steam || {{yes|Operational}} || 55 || {{dts|March 1985}} {{NoteTag|Bottle Rock was re‐commissioned in October 2007 after being brought offline in 1991 by its former owner DWR.}} {{dts|October 2007}} || |- | Aidlin || Calpine 1 || Dry steam || {{yes|Operational}} || 20 || {{dts|May 1989}} || |- | Bear Canyon || Calpine 2 || Dry steam || {{yes|Operational}} || 20 || {{dts|September 1988}} || |- | Sonoma || Calpine 3 || Dry steam || {{yes|Operational}} || 78 || {{dts|December 1983}} || |- | West Ford Flat || Calpine 4 || Dry steam || {{yes|Operational}} || 27 || {{dts|December 1988}} || |- | rowspan=2| McCabe || Calpine 5 || Dry steam || {{yes|Operational}} || 55 || {{dts|April 1971}} || |- | Calpine 6 || Dry steam || {{yes|Operational}} || 55 || {{dts|April 1971}} || |- | rowspan=2| Ridge Line || Calpine 7 || Dry steam || {{yes|Operational}} || 55 || {{dts|July 1972}} || |- | Calpine 8 || Dry steam || {{yes|Operational}} || 55 || {{dts|July 1972}} || |- | rowspan=2| Fumarole || Calpine 9 || Dry steam || {{partial|Offline since 2001}} || 55 || {{dts|November 1973}} || |- | Calpine 10 || Dry steam || {{partial|Offline since 2000}} || 55 || {{dts|November 1973}} || |- | Eagle Rock || Calpine 11 || Dry steam || {{yes|Operational}} || 110 || {{dts|December 1975}} || |- | Cobb Creek || Calpine 12 || Dry steam || {{yes|Operational}} || 110 || {{dts|August 1979}} || |- | Big Geysers || Calpine 13 || Dry steam || {{yes|Operational}} || 60 || {{dts|April 1980}} || |- | Sulfur Springs || Calpine 14 || Dry steam || {{yes|Operational}} || 114 || {{dts|February 1980}} || |- | PG&E 15 {{NoteTag|Calpine never renamed PG&E 15 due to its decommissioning two years before being acquired from PG&E and Unocal Geothermal.}} || Calpine 15 || Dry steam || {{no|Decommissioned}} || 62 || {{dts|June 1979}} || 1997 (Dismantled) |- | Quicksilver || Calpine 16 || Dry steam || {{yes|Operational}} || 119 || {{dts|October 1985}} || |- | Lake View || Calpine 17 || Dry steam || {{yes|Operational}} || 119 || {{dts|November 1982}} || |- | Socrates || Calpine 18 || Dry steam || {{yes|Operational}} || 119 || {{dts|November 1983}} || |- | Calistoga || Calpine 19 || Dry steam || {{yes|Operational}} || 80 || {{dts|March 1984}} || |- | Grant || Calpine 20 || Dry steam || {{yes|Operational}} || 119 || {{dts|October 1985}} || |- | Buckeye || Calpine || Dry steam || {{planned|Planned}} || ? || TBD || |- | Wild Horse || Calpine || Dry steam || {{planned|Planned}} || ? || TBD || |- | rowspan=2| Coldwater Creek || CCPA 1 || Dry steam || {{no|Decommissioned}} || 65 || {{dts|May 1988}} || 2000 (Dismantled) |- | CCPA 2 || Dry steam || {{no|Decommissioned}} || 65 || {{dts|October 1988}} || 2000 (Dismantled) |- | rowspan=2| NCPA 1 & 2 || NCPA 1 || Dry steam || {{yes|Operational}} || 55 || {{dts|February 1983}} || |- | NCPA 2 || Dry steam || {{yes|Operational}} || 55 || {{dts|February 1983}} || |- | rowspan=2| NCPA 3 & 4 || NCPA 3 || Dry steam || {{yes|Operational}} || 55 || {{dts|November 1985}} || |- | NCPA 4 || Dry steam || {{yes|Operational}} || 55 || {{dts|November 1985}} || |- | TBD || Ormat || Dry steam || {{planned|Planned}} || 30 || TBD || |- | rowspan=2| PG&E 1 & 2 || PG&E 1 || Dry steam || {{no|Decommissioned}} || 12 || {{dts|September 1960}} || 1993 (Dismantled) |- | PG&E 2 || Dry steam || {{no|Decommissioned}} || 14 || {{dts|September 1960}} || 1993 (Dismantled) |- | rowspan=2| PG&E 3 & 4 || PG&E 3 || Dry steam || {{no|Decommissioned}} || 28 || {{dts|March 1963}} || 1995 (Dismantled) |- | PG&E 4 || Dry steam || {{no|Decommissioned}} || 28 || {{dts|March 1963}} || 1995 (Dismantled) |} {{NoteFoot}}

==Seismicity== For the past several decades, small earthquakes (less than 2.0) are regularly recorded in the area.<ref>{{Cite web|url=http://scedc.caltech.edu/recent/Maps/San_Francisco.html|title = List of Earthquakes for San Francisco}}</ref> It has been estimated that 99% of all seismic activity at and surrounding The Geysers is around 3.0 or smaller. In fact, "the frequency of seismic events greater than 3.0 have been trending downward since 1990". Due to the remote location it is very infrequent for humans to feel the effect of this tectonic shake. Typically seismic activity in this area is measured using seismometers that can pick up on micro seismicity down to extremely minute levels.<ref>{{Cite web |title=Seismicity |url=https://geysers.com/seismicity |access-date=2022-12-06 |website=geysers.com}}</ref> This has been demonstrated to be caused by the water injection process used to produce the geothermal electricity at the power plant.<ref>{{Cite web |title=Why are there so many earthquakes in the Geysers area in Northern California? |url=https://www.usgs.gov/faqs/why-are-there-so-many-earthquakes-geysers-area-northern-california?qt-news_science_products=0#qt-news_science_products}}</ref>

According to the Lawrence Berkeley National Laboratory Earth Sciences division, seismicity was very low prior to the use of the Geyser steam field for geothermal energy, although this may have been the result of low seismic coverage of the area.<ref name="EGS">{{cite web|title=EGS: The Geysers: What is the history of seismicity at The Geysers?|url=http://esd.lbl.gov/research/projects/induced_seismicity/egs/geysers_history.html|work=Induced seismicity|publisher=Lawrence Berkeley National Laboratory, Earth Sciences Division|access-date=February 9, 2014}}</ref> Before 1969, there were no earthquakes above magnitude 2 recorded by the United States Geological Survey (USGS) in an approximately {{convert|70|mi2|km2}} area around the Geysers.<ref name="EGS" /> Studies have shown that injecting water into the Geysers field produces earthquakes from magnitude 0.5 to 3.0, although a 4.6 occurred in 1973 and magnitude four events increased thereafter.<ref name="EGS" /> Even with increasing injection rates over time, the rate of magnitude 3 earthquakes has remained relatively unchanged since the 1980s,<ref name="EGS" /> although the absolute number of earthquakes has increased significantly.<ref name="SAE" /> A magnitude 4.5 earthquake struck near the Geysers on January 12, 2014, and a magnitude 5.0 on December 14, 2016.<ref>{{cite web|title=M4.5 - 6km NW of The Geysers, California|url=https://earthquake.usgs.gov/earthquakes/eventpage/nc72141176#summary|publisher=United States Geological Survey|access-date=February 9, 2014}}</ref> A magnitude 3.8 earthquake, with a hypocenter 600 meters directly under the field, struck in the early hours of March 3, 2022.<ref>{{cite web|title=M 3.8 - 0km WNW of The Geysers, CA|url=https://earthquake.usgs.gov/earthquakes/eventpage/nc73700486/executive|publisher=United States Geological Survey|access-date=March 3, 2022}}</ref> Despite the increases in the number of earthquakes and the fears of local residents, it is unlikely that a large earthquake will occur at the Geysers since there is no fault or fracture nearby.<ref name="SAE" />

==Geochemistry== In 2005, abatement equipment was installed at two plants to reduce the amount of mercury released via waste vapor even though the amount released was below the legal limit for such releases.<ref name="GeoEnergy" /> The Geysers Air Monitoring Programs has shown limited releases of arsenic, but again below a significant level.<ref name="GeoEnergy" />

==Production== Power plants at the Geysers are of the dry steam power plant type, where the steam directly powers the generator.<ref name="GeoEnergy" /> In general, the Geysers has {{nowrap|1517 MW}}<ref>{{cite book|author=Ronald DiPippo|title=Geothermal Power Plants: Principles, Applications, Case Studies and Environmental Impact|url=https://books.google.com/books?id=YsSN8gdqKWEC|year=2008|publisher=Elsevier Science & Technology|isbn=978-0-7506-8620-4}}</ref> of active installed capacity with an average production factor of 63% (835 MW).<ref>{{Citation | first1 = John W. | last1 = Lund | first2 = R. Gordon | last2 = Bloomquist | first3 = Tonya L. | last3 = Boyd | first4 = Joel | last4 = Renner |title = The United States of America Country Update| url = http://www.osti.gov/geothermal/servlets/purl/895237-Vp8ett/895237.pdf | series = Proceedings World Geothermal Congress | date = 24–29 April 2005 | place = Antalya, Turkey | access-date = 2009-11-09}}</ref>

Of nearly two dozen active plants in the Geysers in 2014, Calpine operated 19 plants in 2004<ref>{{cite book|author=Ann Chambers|title=Renewable Energy in Nontechnical Language|url=https://books.google.com/books?id=GkiMm9fbt7MC&pg=PA143|year=2004|publisher=PennWell Books|isbn=978-1-59370-005-8|pages=143–}}</ref> but only 15 in 2013.<ref>{{cite news|last=Wilkison|first=Brett|title=Sonoma Clean Power makes deal with Geysers operator|url=http://www.pressdemocrat.com/article/20131115/articles/131119694|access-date=February 9, 2014|newspaper=Santa Rosa Press Democrat|date=November 15, 2013}}</ref> Two other plants are owned jointly by the Northern California Power Agency and the City of Santa Clara<ref>{{cite news|last=Baker|title=Steamy industry may clear the air / Geothermal energy producers try to develop more plants -- and more public awareness|url=http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2007/01/14/BUGV2NHQP61.DTL |archive-url=https://archive.today/20120909075702/http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2007/01/14/BUGV2NHQP61.DTL |url-status=dead |archive-date=September 9, 2012 |newspaper=San Francisco Chronicle |location=Lake County |date=January 14, 2007 |page=F-1 |access-date=November 11, 2009}}</ref>

In July 2009, AltaRock Energy planned to drill more than {{convert|2|mi|km}} down to create an "enhanced geothermal" project which was abandoned when federal agencies asked for review.<ref name="SAE" />

==Geology== {{multiple image |image1 = The Geysers geologic features.png |image2 = The Geysers geologic structure.png |footer = Geologic features of The Geysers geothermal area |total_width = 440 }} The Geysers is located on the northeast limb of the Mayacamas anticline, bounded by the Collayomi Fault on the northeast and the Mercuryville Fault on the southwest. The central and eastern Franciscan belts form the core of this anticline. Within this belt is a rock unit forming the reservoir rock, consisting of a sheared and fractured graywacke.<ref name="hardrock" />

A large Bouguer Gravity anomaly combined with slower seismic velocities, located below the Clear Lake Volcanic Field, suggests a magma body is heating the geothermal area.<ref name="hardrock">{{ cite book |last1=McLaughlin |first1=Robert |editor1-last=McLaughlin |editor1-first=Robert |editor2-last=Donnelly-Nolan |editor2-first=Julie |title=Tectonic Setting of Pre-Tertiary Rocks and Its Relation to Geothermal Resources in the Geysers-Clear Lake Area, in Research in the Geysers-Clear Lake Geothermal Area, Northern California, USGS Professional Paper 1141 |date=1981 |publisher=US Government Printing Office |location=Washington |pages=9–11}}</ref>

==See also== {{Portal|California|Geology|Renewable energy}} * List of geothermal power stations in the United States * List of power stations in California

==References== {{Reflist}}

==External links== {{Commons category|The Geysers}} *{{cite book|author=Jeremy Shere|title=Renewable: The World-Changing Power of Alternative Energy|url=https://archive.org/details/renewableworldch0000sher|url-access=registration|date=November 26, 2013|publisher=St. Martin's Press|isbn=978-1-250-03822-7|pages=[https://archive.org/details/renewableworldch0000sher/page/151 151]–}} *{{cite web|title=EGS: Interactive, Real-Time Map of Earthquakes at The Geysers|url=http://esd.lbl.gov/research/projects/induced_seismicity/egs/geysers.html|work=Induced Seismicity|publisher=Lawrence Berkeley National Laboratory, Earth Sciences Division|access-date=February 9, 2014}} *{{cite report|title=A Geysers Album: History of The Geysers Geothermal field.|publisher=California Department of Conservation. Division of Oil, Gas, and Geothermal Resources|year= 1992|url=https://archive.org/details/gov.ca.cdc.doggr.2.7}} *{{cite book|title=U.S. Geological Survey Professional Paper|url=https://books.google.com/books?id=fEzwAAAAMAAJ&pg=SL3-PA74|year=1996|publisher=U.S. Government Printing Office|pages=3–}}

{{DEFAULTSORT:Geysers, The}} Category:Hot springs of California Category:Mayacamas Mountains Category:Geothermal power stations in California Category:California Coast Ranges Category:Geology of Mendocino County, California Category:Geology of Sonoma County, California Category:Geography of Lake County, California Category:Energy infrastructure completed in 1960 Category:Buildings and structures in Sonoma County, California Category:Geography of the San Francisco Bay Area Category:Energy in the San Francisco Bay Area Category:1921 establishments in California